Method of making alpha collet



p 1932- I E. 1. CYIONNELL 1,854,825

METHOD OF MAKING A COLLET Filed May 31, 1930 5 Sheets-Sheet l A ril 19, 1932. E, CONNELL 1,854,825

METHOD OF MAKING A COLLET Filed May 31, 1930 s Sheets-Shet 2 April 19532- E. L CONNELL 1,854,825

. I METHOD OF MAKING A CQLLET Filed May 31, 1930. 3 Sheets-Sheet 3- 127G125 65 I W %@@,W6W

Patented Apr. 19, 1932 I umrso STATES PATENT orrlcs ED'WIZN' L. CONNELL, OF CLEVELAND HEIGHTS, OHIO, ASSIGNOB T VAN IDOBZN' ELEC- I TRIO TOOL COMPANY, OF CLEVELAND, OHIO, A. CORPORATION 01' OHIO unrnon or MAKING A ooLnEr Application filed Kay 31, 1930. Serial 110. 457,999.

This invention relates to the improvement of collets and an improved method of manufacturing the same. A collet of the type to which this invention relates usually consists of a split tube or sleeve, which has tapering or conical ends that fit intoseats having a corresponding taper, so that a lengthwise movement of one of the seats causes a contraction or expansion of both ends of the collet.

One of the objects of the invention is to provide a collet adapted to rip objects which vary through a consideraifle range of diameters, such as stems of automobile valves, while positioning the object for rotation with the utmost de cc of axial precision.

A further 0 ject is to provide an economical method of manufacturing a collet whereby the product will be extremely accurate and flexible.

Another object is the revision of a method ofimanufacturing a col et, of the double end split form, whereby the bore may be accurately ground after hardening, and wherein the hardening and tempering operation may be performed without necessitating the use of a mandrel, arbor or other similar fixture.

Another object is to provide a collet of such a typethat a minimum circumferential surface or frictional area thereof will remain in contact with the collet retaining seats for all contracted or work holding positions of the collet, maintaining accurate axial alignment of the work.

Further objects of the invention will become apparent from the specification, and a preferred method and embodiment will be illustrated in the drawings. The essential novel characteristics will be set forth in the claims.

In the drawings, Figs. 1and2illustrate different forms of bar stock which are used in the manufacture of the collet; Figs. 3 and 4 are transverse sections and are indicated by the lines 3-3 and 4-4 in Figs. 1 and 2, respectively; Fig. 5 is a transverse section through a tubular bar stock, which may be used for the manufacture of a collet; Figs. 6 and 7 are perspectives, partially broken away, and illustrate the collet in one stage of manufacture; Figs. 8 and 9 are transverse sections and are indicated by the lines 8-8 and 9-9 on Fi s. 6 and 7, respectively; Fig. 10 illustrates the blank after the slots have been formed therein; Fig. 11 is a horizontal section and is indicated by the line, 11-11. on Fig. 10; Figs. 12, 13 and 14 are transverse sections, and are indicated by the lines 12-12, 13-13, 14-14, respectively, on Fig. 10; Fig. 15 is a perspective of a slotted blank which has been made from hexagonal bar stock; Fig. 16 is a transverse section, and

is indicated by the line 16-16 on Fig. 15';

Fi 17 is a perspective of a blank, ready to be ardened; Fig. 18 is a horizontal section and is indicated by the line 18-18 on 17; Fig. 19 is a transverse section as in cated by the line 19-19 of Fig. 17; Fi 20 illustrates a number of blanks su orte for hardening; Fig. 21 illustrates a blank bein tempered; Figs. 22 and 23 are longitudin sections, and illustrate various grinding operations; Fig. 24 is an end elevation of.v a finished collet; Fig. 25 is a longitudinal sec-. tion illustrating a collet in use; Fig. 26 is an end elevation on an enlarged scale of a collet, in a contracted position; Fig. 27 is a. fragmentary section through the collet in a contracted position, and is indicated by the line 27-27 in Fig. 26.

Heretofore collets have been produced by boring bar stock which has been cut to. the required length, then slotting the tube lengthwise from opposite ends, the alternate slots breaking through the alternate ends of the blank and providing open-end slots. The outer edges and the internal gripping portions of the blank were then ground to a high degree of accuracy. The blank was then clamped to a hollow arbor, with the ends of the blank being rigidly confined therein. While the blank was so confined, it was hardened and tempered, and then removed from the arbor as a finished or completed collet. This method produces a collet which will grip materials and retain them in accurate axial alignment at the time of their removal from the arbor. However, it has been found that this method is expenslve and frequently I 1t occurs that after the collet has been removed from the arbor a considerable length of time, it has a tendency to warp, due to the strains set up in the grain of the metal, while confined in the arbor during the hardening and tempering operation.

y improved method of manufacturing a collet comprises in general the cutting of the blank from suitable bar stock, then boring the blank and tapering its ends in an automatic screw machine, thereafter undercutting the middle portion and reaming the end portions of the internal surfaces of the blank, thereafter cutting slots through the walls of the blank, intermediate its ends, and flattening the end portions of the blank adjacent alternate slots. I then harden and temper the blank without the use of a fixture, before grinding, and while the slots are still joined on both ends by metal of the blank. Hence, because the blank is not clamped in a fixture of any sort. the natural grain of the metal will be undisturbed. Thereafter, the ends of the collet are ground, and finally the metal is removed from alternate ends to the alternate slots, thereby finishing the collet.

Referring to the drawings, Figs. 1 to 5 inclusive illustrate suitable bar stock fro-m which the collet is to be made. The stock may be a substantially round and solid bar, as shown at 10, in Fig. 1, or a bar having a polygonal section, as indicated by the hexagonal bar 12, in Fig. 2. However, tubing, such as is illustrated at 14, in Fig. 5. may likewise be used. When solid bar stock, such as shown in Figs. 1 and 2, is used, it must be rough bored, while when tubing is used, this operation is not required.

The boring operation may conveniently be accomplished on an automatic screw machine, which will also rough form the stock into blanks of the proper length, shape and taper the ends of the blank, as shown at in Fig. 6. If desired, the outer surface of the blank may be undercut, as shown at 16, thereby reducing the sectional area throughout the middle portion of the blank to increase flexibility, as will be hereinafter explained. lVhen hexagonal bar stock is used, the undercutting will comprise the removing'of the hexagonal corners from the central portion thereof.

After the blank has been rough bored, cut, tapered and the surface undercut, it is removed from the automatic screw machine and placed in a fixture to be internally recessed and reamed. In this operation, the internal surface of the blank is reamed, as indicated at 18 and 19, and undercut, as indicated at 20 in Fig. 6. This lightens the wall of the blank, so that the finished collet will be resilient, and at the same time maintains the rigidity of the metal in the end portions of the blank, thereby giving strength to the jaws of the finished collet.

The walls of the collet are next slotted. As

shown in the Figs. 10 to 17 longitudinally extending slots are milled or otherwise cut through the walls of the blank, parallel with the axis thereof, and equi-distant from each other. In case the hexagonal bar stock is used, the slots are cut at the corners of the bar. It will be noted that the slots 25 are so cut that they do not break through the ends of the blank, but leave substantial bridges 26 at one end of the blank, and comparatively slight bridges 27 at the other end. The slots are so arranged that the bridges 26 and 27 alternate at each end of the collet. In this manner the ends of the collet blanks are left substantially solid for the succeeding operations.

The tapered ends 15 of the blank comprise the surfaces which, in the finished collet, coact with spindle sockets to contract or expand the jaws of the collet. It has been found that greater accuracy can be obtained in the functioning of the collet by decreasing the area of this tapered surface 15, as this reduces the frictional contact between the collet and the seats, due to a reduction in the length of the area of contact of each jaw. To this end surfaces 30 are next milled at each end of the collet. As shown in the drawings, there are three such surfaces or flats for each end of the blank, one flat for each alternate slot 25 on each end of the blank. Each flat 30 in a plane normal to the plane of its corresponding slot. which plane intersects the conical or tapered surface 15 and the axis extended of the blank. This operation materially reduces the tapered area of the blank, as well as further decreases the material in the bridge 27. but not eliminating the latter entirely.

When hexagonal or similar shaped bar stock is used, the milling of the flats 30 are not required as the normally flat sides 31 meterially reduce the tapered portion 15 as indicated at 32 on Fig. 15.

As the collet is required to grip objects which vary throughout great ranges of sizes or diameters, it must be extremely flexible, and therefore requires the use of a grade of steel which can be hardened and tempered. Immediately following the operation of milling the flats 30 on the ends of the blank B it is hardened. In the hardening step, as illustrated in Fig. 20, the blanks are preferably suspended from a suitable support 35 by wires 36, which pass through the slots 25 and are twisted about the support. The support carrying the blanks is then placed in a muffle or other similar container 37, and subjected to heat to bring the blanks to the proper temperature for hardening. As the slots are joined at each end by the bridges 26 and 27, there is practically no tendency for the blank to warp. Therefore, the hardening operation does not require the use of mandrels, arbors or other similar fixtures. I-Ieretofore, the practice has been, especially in the manufacture of double-ended split collets, to harden the blank while it is held by an arbor or fixture, because the slots were cut clear through one end of the blank. While in my improved method of manufacture, which comprises hardening the blank while each end of each slot is joined by a suitable bridge, no arbor or fixture is required. Hence, the hardening operation is accomplished with comparatively less expense and made much more simple.

The blank is next polished in any wellknown manner, followed by tempering to give the blank a great degree of flexibility. Again, in the tempering operation, due to the bridges 26 and 27, no arbor or fixture is required. Hence, this operation likewise is accomplished with comparatively small expense, and is made much more simple. As there is no great bulk of material to which the blank is clamped. no false strains are set up within the grain of the metal during the heating operation required for tempering. with the result that the blank remains true and does not warp. The tempering operation may be accomplished manually, as illustrated in Fig. 21, the blank beingheld by suitable tongs over a burner 41, and as substantially the entire blank is visible to the operator, therefore it is easily brought to the proper temper.

The temperingoperation is followed by a grinding operation. The blank is mounted in a suitable fixture, and is internally ground, as at in Fig. 22, and the tapered edges 30 of the ends are also ground, as at 52 in Fig. 22, thereby giving an accurate taper to the bevelled edge of the blank, which taper accurately conforms to the socket members in which the collet is to be positioned. The grinding of the inner surfaces at 50 provides the collet with an accurate gripping surface to retain the work. The blank is then clamped to an arbor 55 by suitable clamps 56 and a grinding wheel 57 grinds away the bridge 27, thereby leaving the ends of the alternate slots on each end of the collet open, as indicated at 57 in Fig. 23 and Fig. 24. The collet is then removed from the arbor, and is ready for use.

The use of the collet is best illustrated in Figs. 25 to 27, inclusive. In these figures. the collet is slidably mounted in a suitable sleeve 60, which has a contracted conical inner end surface member 61 rigid therewith, which member coacts with the bevelled portion 62 of one end of the collet. Slidably mounted in the sleeve is a second sleeve 63, which has a conical formed inner surface 64 adapted to co-act with the bevelled surface 65 of the collet. A suitable plunger 66 threaded into the sleeve 60 urges the sleeve 63 against the plunger, bringing the bevelled surfaces 61 and 64 together, thereby contracting the end of the collet. The plunger 66 is provided with a suitable hand wheel 67, by means of which it may be rotated, within the sleeve 60, to bring the sleeve 63 toward or away from the collet as desired. The sleeve 60 is rotatably mounted in a suitable carriage or head 66, which is provided with the usual work feeding and indexing means, whereby the work. such as an automotive valve 70, may be placed in proper relation to a tool, such as a grinding wheel (not shown). The sleeve 60 is provided with a suitable pulley 71 rigid- 1y secured thereto, by means of which the sleeve, with its associated collet and work, may be rotated.

It will be seen from the foregoing description, that I have provided a collet which is extremely accurate and wherein the grain in the metal thereof is natural and has been undistorted by the hardening and tempering opera'tions during the course of its manufacture. I have also provided a collet wherein the surfaces which contact with the sockets, in which the collet is used, have the minimum frictional. area of contact, which is consistent witheffective operation of the collet. I have also provided a method of manufacture of the collet wherein the collet may be hardened and tempered without the use of fixtures and the grinding of the seats and work gripping jaws of the collet may be ground after the hardening and tempering operations have been completed.

I claim 1. The method of manufacturing a collet which comprises metallurgically treating ablank slotted intermediate itsends to enhance the flexibility of the intermediate portions of the finished product and thereafter removing the metal from one end of each slot.

2. The method of manufacturing a collet, which comprises slotting a metal tube, said slots being bridged at their ends by the metal of the tube, hardening the slotted tube without the use of a mandrel, and thereafter removing the metal from one end of each slot.

3. The method of manufacturing a collet, which comprises slotting a metal tube, said slots bridged at their ends by metal of the tube, tempering the slotted tube without the use of a fixture, thereafter grinding the outer end surfaces of the tube and removing the metal from alternate ends of alternate slots.

4. The method of manufacturing a doubleended split collet, which comprises cutting bar stock into blanks of a predetermined length, boring the blanks and tapering the ends thereof, slotting the blanks, said'slots terminating a pre-determined distance from each end of the blank, bevelling themetal of the blanks adjacent alternate ends of alternate slots in a plane normal to the axis of the slot and intersecting the axis extended of the blank.

5. The method of manufacturing a doubleended split collet, which comprises cutting bar stock into blanks of pro-determined lengths, boring the blanks and tapering the ends thereof, slotting the blanks, said slots terminatin a predetermined distance from each end or the blank, bevellin the metal of the blanks adjacent one end of each slot and in a plane normal to the axis of the slot and intersecting the axis extended of the blank, suspending the blank While subjecting it to a hardening heat, thereafter grinding the taper on the ends, grinding the internal bore, and finally removing the metal from the one end of each slot.

6. The method of manufacturing a doubleended split collet, which comprises cutting bar stock into blanks boring the blanks and tapering the ends thereof, slotting the blanks, said slots being bridged at their ends by the metal of the blank, flattening the ends of the blanks adjacent alternate slots, said flats being in planes normal to the axis of the corresponding .slots and intersecting the axis extended of the blank, suspending the blank without the use of a fixture While hardening.

and tempering the blank, thereafter grinding the taper on the ends and the internal bore,

and finally removing the bridges from the end of each slot adjacent its corresponding flattened surface.

Intestimony whereof, I herennto aifix my signature.

EDWIN L. CONNELL. 

